The packing densities of semiconductors have been increasingly made larger and in recent years, 3D multilayering technologies have remarkably evolved. In particular, the TSV (Through Si Via) technologies are expected as the next generation's semiconductor multilayering technologies. The dimensions of each TSV are 20 μm in diameter and approximately 80 μm in depth and TSVs. are minute and high in aspect ratio as compared with microbumps now in wide use in 3D lamination. For this reason, a void that may be produced when TSVs. are formed by Cu plating is prone to be a critical defect and there are the high needs for inspection for voids in TSV. In one of void detection technologies in wide use, an X-ray is applied to a semiconductor wafer (hereafter, referred to as wafer) and an analysis is made on a resulting transmission image and Patent Literature 1 describes a technology in which a wafer surface is irradiated with an X-ray from a direction inclined from the perpendicular direction to detect any void.